The present invention relates to a heat exchanging fin and a die-punch set for manufacturing the heat exchanging fin, more precisely relates to a heat exchanging fin having a plurality of collars, which enclose through-holes in a plate section and through which heat exchanging tubes will be pierced, and a die-punch set for manufacturing said heat exchanging fin.
The heat exchanging fin 10, which is employed in an air conditioner, etc., is shown in FIG. 9. The heat exchanging fin 10 includes: a belt-like thin plate section 11, which is made of a metallic thin plate, e.g., aluminium thin plate; a plurality of through-holes 12; and a plurality of collars 14, each of which extends upwardly from an edge of each through-hole 12. Namely, a plurality of collars 14 are linearly arranged in the longitudinal direction of the belt-like thin plate section 11. There is formed a flange 15 at an upper end of each collar 14.
The heat exchanging fins 10 are usually manufactured by a drawless manner (see FIGS. 10A-10D). In the drawless manner, firstly small through-holes 101 are formed in the thin plate by pierce machining (see FIG. 10A. Edges 102 of the small through-holes 101 are upwardly bent by burring so as to form them into projected sections 103 (see FIG. 10B). Then the projected sections 103 are upwardly squeezed by squeezing so as to form the collars 104 (see FIG. 10C). Finally, the flange 105 is formed at the upper end of each collar 104 by flare machining (see FIG. 10D).
The heat exchanging fins 10 are piled as shown in FIG. 11. Then, a heat exchanging tube 16, which is made of a metal having high heat conductivity, e.g., copper, is pierced through the through-holes 12 of the heat exchanging fins 10, which have been coaxially arranged. Since the flanges 15 respectively contact a bottom face of the heat exchanging fin 10 on the upper side, spaces are kept between the adjacent heat exchanging fins 10. Namely, the heat exchanging fins 10 are mutually separated with the distance equal to the height of the collars 14.
There are formed spaces 12a between an outer circumferential face of the heat exchanging tube 16 and inner circumferential faces of the collars 14, so the heat exchanging tube 16 is expanded by inserting an expanding bullet 17. By inserting the expanding bullet 17 into the heat exchanging tube 16, the heat exchanging tube 16 can be integrated with the collars 14 of the heat exchanging fins 10, so that the heat exchanging ability can be raised.
In some cases, the separation between the adjacent heat exchanging fins 10 is made wider by forming higher collars 14. Since the collars 14 are formed by squeezing the projected sections which extend from the edges of the through-holes 12, the thickness of the collars 14 is made thinner if the collars 14 are made higher.
In the case of providing thin collars 14, the flanges 15 are apt to be broken as shown in FIG. 12. Note that, a broken part is indicated by numeral 19.
If the thickness of base ends of the collars 14, which connect the collars 14 with the plate section 11, is very thin, the collars 14 are apt to be deformed when the heat exchanging tubes 16, which have been pierced through the collars 14, are integrated with the heat exchanging fins 10 by inserting the bullet 17. If the collars 14 are deformed, the adjacent fins 10 mutually contact and the distance therebetween is not fixed (see FIG. 13), so that the heat exchanging ability is reduced.
The broken flange 19 and the mutual contact between the adjacent heat exchanging fins 10 are apt to occur in the very thin heat exchanging fins 10. However, these days thinner heat exchanging fins 10 are required to provide lighter heat exchangers.